In wireless communications systems, the mobile receiver (such as a cell phone) can experience significant variations in the received signal strength of a signal that is transmitted by the base station transmitters. It is not unusual to experience a 70 dB variation from the strongest to the weakest signal strength. The variation is due to various factors, including the varying distance between the mobile receiver and the a base station, Rayleigh fading, and other operational variances.
Thus, the mobile receiver should have a means for compensating for this wide variation in received signal strength. In some mobile receivers, an automatic gain control circuit is used. While these circuits can be useful, they are still unable to fully compensate for the dynamic range in the received signal. For example, in the Global System for Mobile Communications (GSM) standard for digital cellular telephony, interleaving of data is employed. Because of this interleaving, a slow AGC is typically employed that cannot fully compensate for the full range of variation.
If the dynamic range of the received signal is not adequately compensated, this will significantly increase the difficulty in signal processing by the base band digital receiver, or will result in signal degradation due to saturation or truncation error.